Telemetry System, a Pipe and a Method of Transmitting Information

ABSTRACT

The invention relates to a telemetry system for use in a pipe having a wall, comprising a transmitter adapted to generate at least one acoustic wave in a frequency range of about 50-300 kHz and to inject the acoustic wave in the wall of the pipe, wherein the transmitter is further arranged to binary code information conceived to be transmitted with the acoustic wave. The invention further related to a pipe comprising the telemetry system and to a method of transmitting information via a pipe.

FIELD OF THE INVENTION

The invention relates to a telemetry system for use in a pipe having awall.

The invention further relates to a pipe.

The invention still further relates to a method of transmittinginformation through a pipe.

BACKGROUND OF THE INVENTION

An embodiment of a pipe as is set forth in the opening paragraph isknown from EP 2 157 279. the known pipe comprises a transmitter forgenerating an acoustic signal with a frequency of a few kHz at a firstlocation near a distal portion of the pipe, a receiver located at afurther position in the pipe for receiving the acoustic signal and forattempting to synchronize the receiver at the transmitter frequency anddepending on a success of the synchronization step either to carry ondata transmission or to adjust the transmission frequency.

It is a disadvantage of the known pipe that due to reflections in thejoints of the segmented pipe only a limited frequency bands around about2-3 kHz can be used. This has a further disadvantage that lowfrequencies limit data transmission rates considerably, which is notdesirable.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved pipe and atelemetry system for use with the pipe enabling data transmission withincreased transmission rates, wherein such transmission is reliable andsubstantially error-free.

To this end the telemetry system for use in a pipe having a wallcomprises a transmitter adapted to generate at least one acoustic wavein a frequency range of 50-300 kHz and to inject the acoustic wave inthe wall of the pipe, wherein the transmitter is further arranged tobinary code information conceived to be transmitted with the acousticwave. It will be appreciated that for the pipe a drill pipe may beselected. It is found that the frequency range of 50-300 kHz isparticularly suitable to accommodate a wall thickness range which may beused for industrial pipes.

It is found that for a transmission using ultrasound waves propagatingin a wall of a pipe, a characteristic parameter (P) for ultrasonicinformation transfer depends on a wave number multiplied by wallthickness of a pipe. This variable (P) should be minimized because forsuch variables having a high value the attenuation of the signal in thematerial of the pipe increases accordingly:

${P = {\frac{2\pi \; f}{C_{s}}\frac{D}{2}}},$

wherein

f is the frequency of the acoustic wave propagating in a wall of thepipe;

Cs is the shear velocity of the acoustic wave;

D is a thickness of the wall.

However, it is noted that the phase velocity of the acoustic wavedecreases with increasing the parameter (P). In addition, for highvalues of the parameter (P) higher ultrasound frequencies may be usedwhich enable use of higher data transmission rates.

The invention has an advantage that no carrier wave is used. Theinformation conceived to be transmitted using the ultrasound waves isbinary coded using a pre-determined rule for the multiple frequencies ofthe generated ultrasound waves. It is further found that using thefrequency range of 50-300 kHz high information rate may be achieved,especially with respect to the carrier frequencies below 40 Hz. Inaddition, it is found that there is a substantial reduction of parasiticnoise in the frequency range of 50-300 kHz. Still further, it is foundthat a smaller design of the apparatus is feasible when the transduceris tined to the higher frequencies, i.e. the frequencies above 50 kHz.

For example, separate frequencies may be switched on/off for dataencoding according to the following exemplary rule: 50kHz=1; 51 kHz=0;52 kHz=1, etc., that is even frequencies are assigned the logic 1 andodd frequencies are assigned the logic 0.

Alternatively, it is also possible to assign frequency groups, such aspairs, for coding. For example pairs (50, 51) kHz, (52, 53) kHz, etc.may be used for binary coding information conceived to be transmitted sothat only one frequency from the pair is transmitted. According to arule, when 50 kHz is received, the bit equals to 0, when 51 is received,the bit equals to 1, etc. When none of the frequencies from the assignedpairs (or larger groups) is received the threshold can be adapted toreceive either of the two. This method can be used for overcoming false0 and to increase confidence in data transfer at a cost of data rate.

In a particular embodiment of the telemetry system according to theinvention the acoustic wave is a L(0, 2) or T(0, 1) wave.

In particular, it is found that the L(0, 2) wave is particularly usefulbecause the particle motion in this wave is mainly longitudinal whichcauses a low liquid coupling (i.e. low attenuation) and a good couplingbetween the successive segments of the pipe.

In a further embodiment of the telemetry system according to theinvention the transmitter comprises an array of elements. Piezoelectricelements or elements operating using other technology, such aselectromagnetic acoustic transducers may be used. Preferably, thetransmitter is ring-shaped.

It is found that an array-shaped or ring-shaped embodiment of thetransmitted is useful, as it may be easily integrated between thesegments of the pipe. Usually, the segments are about 10 meter long. Atransmitter operated according to the invention is capable oftransmitting the acoustic waves carrying information through severalsegments. Three to five segments may be transmitted through without aneed for amplification.

Because the pipes are much longer than 30 meters, it may be necessary tobuilt-in an amplifier on a path of the ultrasonic waves emanated fromthe transmitter. For example, the amplifiers may be provided every 3-5segments.

In a further embodiment of the telemetry system according to theinvention, the amplifier is adapted to implement a consistency check ofa received binary code.

Those skilled in the art will readily appreciate which per se knownconsistency check algorithms may be used for this purpose. It will befurther appreciated that such smart logic may form part of theamplifier, or, alternatively, the signal received by the amplifier maybe processed by a dedicated smart logic unit and returned to theamplifier for amplification. For the simplicity reasons, the latterarrangement is referred to as an amplifier.

In a still further embodiment of the telemetry system according to theinvention the amplifier is further arranged to generate an amplifiedfrequency shifted signal.

It is found to be particularly useful to allow a frequency shift of theamplified signal with respect to the signal feeding the amplifier. Forexample, for a first amplifier, receiving the in-frequencies of 50, 51,52, 53, 54 . . . x, kHz, the amplified signal may have the followingfrequencies: 50.1, 51.1, 52.1, 53.1, 54.1, . . . x′ kHz. This feature isfound to be advantageous as interference between the amplified and theincoming signal is substantially avoided.

The pipe according to the invention comprises the telemetry system as isset forth with respect to the foregoing.

The method of transmitting information through a pipe, according to theinvention, comprises the steps of injecting at least one acoustic wavein a frequency range of 50-300 kHz in a wall of the pipe; whereininformation conceived to be transmitted with the acoustic wave is binarycoded. The method is found to be particularly suitable to transmitinformation from a drill location through a drill pipe.

In the preferable embodiments of the method according to the invention,for the at least one acoustic wave a L(0, 2) or a T(0, 1) is selected.The method may further comprise the steps of amplifying a signalgenerated by the transmitter; implementing a consistency check of areceived binary code.

In a still further advantageous embodiment of the method according tothe invention it further comprises the step of frequency shifting anamplified signal with respect to the incoming signal.

These and other aspects of the invention will be discussed withreference to drawings wherein like reference signs correspond to likeelements. It will be appreciated that the drawings are presented forillustrative purposes only and may not be used for limiting the scope ofthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents in a schematic way an embodiment of an overview of adrill set-up.

FIG. 2 presents in a schematic way an embodiment of a telemetry systemaccording to an aspect of the invention.

FIG. 3 presents in a schematic way an embodiment of a ring-shapedtransmitter provided in a joint of a pipe.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 presents in a schematic way an embodiment of an overview of adrill set-up. A drilling installation 10 may be provided forimplementing suitable underground exploration works. For example,drilling for investigating oil bearing strata may be envisaged.

A pipe D, notably a drill pipe, may be used for conducting controlsignals Sin from the control unit to the drill bit 6 and for conductinginformation at least about the drill environment Sout from the drill bit6 up to the control system 3. In according to an embodiment of thetelemetry system according to the invention a pipe D may be providedcomprising a suitable number of pipe segments 4 a, 4 b, 4 c, 4 d, 4 e, 4f, 4 g, 4 h interconnecting a control system 2 located above the groundwith a drill bit 6 located distally. The pipe segments areinterconnected by suitable joints 5 a, 5 b, 5 c, 5 d, 5 e, 5 f, 5 g, 5h. Preferably, the pipe is manufactured from metal. However, othermaterials, such as metal may be used.

In accordance with the invention a telemetry system 7 is providedcomprising a transmitter (not shown) adapted to generate at least oneacoustic wave in a wall of the pipe D, wherein the frequency of the atleast one acoustic wave is in the range of 50-300 kHz and wherein thetransmitter is further arranged to binary code information conceived tobe transmitted using the said at least one wave. It will be appreciatedthat it is found that a single wave mode is sufficient for transmittingthe information using two or more frequencies.

For example, when a single frequency is used the amplitude of theacoustic signal may be used for coding the information into the binarycode. For example, when the amplitude is set above a pre-definedthreshold the value of the byte is 1, otherwise it is 0. Alternatively,a number of frequencies may be used for binary coding the information.As has been explained earlier, a rule can be used for assigning aparticular frequency or frequencies to the value 1 and assigning otherfrequency or frequencies to the value 1.

In accordance with an aspect of the invention, the signal generated bythe transmitter may be amplified by an amplifier provided in one or morejoints of the pipe segments. For example, an amplifier 8 may beinstalled in the joint 5 f to receive the acoustic signal propagating inthe wall of the pipe D, to carry out a consistency check and to generatean amplified signal, which is preferably frequency shifted with respectto the incoming signal. This measure is found to be particularlyadvantageous for preventing undesirable signal interference postamplification.

It will be appreciated that information suitable for transmitting fromthe drill bite towards the control system may be collected by a suitablesensor or sensors arranged on or within the drill bite. This method ofdata collecting regarding particular characteristics of the drillenvironments is known per se and will not be explained here in details.For example, known systems arranged in the drill bite may comprisesensor or sensors adapted to provide information about the drillingprocess and the direction in which the drill bit is propagating. It willbe further appreciated that particularly for exploration of oil bearinglayers in strata drill strings may be quite long, up to severalkilometers, for example.

FIG. 2 presents in a schematic way an embodiment of a telemetry systemaccording to an aspect of the invention. As has been explained earlier,the pipe 20 may comprise a plurality of pipe segments 21 a, 21 b, . . ., 21 n, 21 n+1, joined together. In accordance with the invention thedrill bite 26 comprises a transmit/receive unit 24 arranged to collectcontrol data from the control system for controlling or adjusting thedrill bite and to transmit information data collected by suitable sensoror sensors provided on the drill bite 26 upstream towards the controlsystem. The control system is usually located above the ground. Thetransmitter is adapted to generate at least one acoustic wave in afrequency range of about 50-300 kHz and to inject the acoustic wave inthe wall of the pipe, wherein the transmitter is further arranged tobinary code information conceived to be transmitted with the acousticwave. The acoustic wave or waves will propagate in the direction Pupstream the pipe D towards the control system (not shown). Inaccordance with a further aspect of the invention a suitable pluralityof amplifiers 22 a, 22 b, 22 c is built-in the joints connecting thesegments of the pipe D for amplifying the incoming signal. Preferablysuch amplifiers are arranged with a distance between them of about 3-5meters and are further adapted to carry out a consistency check of theincoming binary word. In addition, for improving the signal transmissionquality, the amplifiers 22 a, 22 b, 22 c may be adapted to frequencyshift the output amplified signal with respect to the input signal.

FIG. 3 presents in a schematic way an embodiment of a ring-shapedtransmitter provided in a joint of a pipe 30. The ring-shapedtransmitter 32 is preferably built-in the pipe segment 33 and iscoaxially arranged with it. The collar 31 which may be used for affixingthe adjacent segments to each other may be used for firmly holding thetransmitter 32. The collar may be provided with a suitable plurality ofaffixing elements 31 a. The ring-shaped transmitter 32 is preferablymanufactured from a piezoelectric material and may be implemented eitheras a continuous material, or as a suitable array of individualpiezoelectric elements. The latter embodiment is advantageous in casethe transmitter 32 is operable for generating a plurality of acousticwaves in the wall of the pipe 33.

While specific embodiments have been described above, it will beappreciated that the invention may be practiced otherwise than asdescribed. Moreover, specific items discussed with reference to any ofthe isolated drawings may freely be inter-changed supplementing eachouter in any particular way. The descriptions above are intended to beillustrative, not limiting. Thus, it will be apparent to one skilled inthe art that modifications may be made to the invention as described inthe foregoing without departing from the scope of the claims set outbelow.

1. A telemetry system for use in a pipe having a wall, comprising atransmitter adapted to generate at least one acoustic wave in afrequency range of about 50-300 kHz and to inject the acoustic wave inthe wall of the pipe, wherein the transmitter is further arranged tobinary code information conceived to be transmitted with the acousticwave.
 2. The system according to claim 1, wherein the acoustic wave is aL(0, 2) or T(0, 1) wave.
 3. The system according to claim 1, wherein thetransmitter comprises an array of elements.
 4. The system according toclaim 3, wherein the transmitter is ring-shaped.
 5. The system accordingto claim 1, wherein the pipe comprises consecutive segments, thetransmitter being adapted to be positioned between the consecutivesegments.
 6. The system according to claim 1, wherein the transmitter isadapted to generate a binary code using pre-defined frequencies of aplurality of the acoustic waves.
 7. The system according to claim 1,wherein the system further comprises an amplifier for amplifying asignal generated by the transmitter, the amplifier being arranged toimplement a consistency check of a received binary code.
 8. The systemaccording to claim 7, wherein the amplifier is further arranged togenerate an amplified frequency shifted signal.
 9. A pipe comprising thetelemetry system according to claim
 1. 10. The pipe according to claim9, forming part of a drill arrangement.
 11. A method of transmittinginformation through a pipe comprising the steps of: injecting at leastone acoustic wave in a frequency range of about 50-300 kHz in a wall ofthe pipe; wherein information conceived to be transmitted with theacoustic wave is binary coded.
 12. The method according to claim 11,wherein for the at least one acoustic wave a L(0, 2) or a T(0, 1) isselected.
 13. The method according to claim 11, further comprising thesteps of: amplifying a signal generated by the transmitter; implementinga consistency check of a received binary code.
 14. The method accordingto claim 13, further comprising the step of frequency shifting anamplified signal.
 15. The method according to claim 11, wherein for thepipe a drill pipe is used.